A virtual image is formed when light rays appear to diverge from a point behind a mirror or lens, even though the rays do not actually converge at that point. It may seem counterintuitive, but virtual images are a result of the way our eyes perceive the path of light rays.
In the case of mirrors, a virtual image is formed when the incident light rays reflect off the mirror's surface. The key point to understand is that the reflected rays appear to originate from a point behind the mirror, but they do not actually pass through that point. When our eyes trace back the paths of these reflected rays, they intersect at a point in space, giving the impression of an image. However, if you were to place a screen at the location where the virtual image appears, you wouldn't see anything because the light rays do not converge there.
Similarly, in the case of lenses, a virtual image is formed when light rays pass through the lens and appear to diverge from a point on the opposite side of the lens. This point is often referred to as the virtual image location. Again, the light rays do not actually converge at that point, but our eyes perceive them as if they do.
Virtual images cannot be projected onto a screen since the rays of light do not physically converge to form a real image. Instead, they are seen by an observer looking through the lens or in the case of mirrors, the observer sees the virtual image by tracing the reflected rays back with their eyes.
It's important to note that virtual images have properties that differ from those of real images. Virtual images are always upright, meaning they have the same orientation as the object, and they are formed when the object is located within the focal length of a converging lens or in front of a concave mirror. Real images, on the other hand, are formed by converging light rays and can be projected onto a screen.